The preparation, purification, and determination of properties of a variety of rare earth porphyrin materials will be undertaken. Both synthetic and mechanistic studies will be employed in determining the optimum methods for preparing and handling such materials for employment as molecular biological probes. Their spectroscopic, magnetic, and emission properties would allow them to serve as rather unique probes. They may be used to probe various aspects of hemeprotein phenomena, the photodynamic action of porphyrins in porphyrias, the membrane activity of porphyrins in certain neoplasias, and the role of antenna versus active site chlorophyll in photosynthesis. The initial synthetic studies will mainly employ spectrophotometric, chromatographic, and analytical methods, while the later probe studies will entail EPR and fluoresence measurements as well.